electrostatographic toner particle comprising a polyester containing a covalently bound quaternary phosphonium salt

ABSTRACT

New electrostatographic toners and developers are provided, containing dual function polyester binder/charge agents. The new toner particle has an average diameter in the range of 0.01 to 100 micrometers and comprises a binder polyester and a charge-control agent comprising a quaternary phosphonium salt, wherein the phosphonium salt has a cationic portion comprising a phosphorus atom covalently bonded to at least one moiety containing an ester linkage to the binder polyester.

FIELD OF THE INVENTION

This invention relates to electrostatographic toner particles comprisingpolyester binders. More particularly, the invention concerns new tonerparticles comprising polyesters containing certain quaternaryphosphonium salts, wherein at least the cationic portions of the saltsare covalently bonded to the polyesters through ester linkages. Thepolyesters serve as dual function binder/charge agents in the inventiveelectrostatographic toner particles.

BACKGROUND

In electrostatography an image comprising an electrostatic fieldpattern, usually of non-uniform strength, (also referred to as anelectrostatic latent image) is formed on an insulative surface of anelectrostatographic element by any of various methods. For example, theelectrostatic latent image may be formed electrophotographically (i.e.,by imagewise photo-induced dissipation of the strength of portions of anelectrostatic field of uniform strength previously formed on a surfaceof an electrophotographic element comprising a photoconductive layer andan electrically conductive substrate), or it may be formed by dielectricrecording (i.e., by direct electrical formation of an electrostaticfield pattern on a surface of a dielectric material). Typically, theelectrostatic latent image is then developed into a toner image bycontacting the latent image with an electrostatographic developer. Ifdesired, the latent image can be transferred to another surface beforedevelopment.

One well-known type of electrostatographic developer comprises a drymixture of toner particles and carrier particles. Developers of thistype are commonly employed in well-known electrostatographic developmentprocesses such as cascade development and magnetic brush development.The particles in such developers are formulated such that the tonerparticles and carrier particles occupy different positions in thetriboelectric continuum, so that when they contact each other duringmixing to form the developer, they become triboelectrically charged,with the toner particles acquiring a charge of one polarity and thecarrier particles acquiring a charge of the opposite polarity. Theseopposite charges attract each other such that the toner particles clingto the surfaces of the carrier particles. When the developer is broughtinto contact with the latent electrostatic image, the electrostaticforces of the latent image (sometimes in combination with an additionalapplied field) attract the toner particles, and the toner particles arepulled away from the carrier particles and become electrostaticallyattached imagewise to the latent image-bearing surface. The resultanttoner image can then be fixed in place on the surface by application ofheat or other known methods (depending upon the nature of the surfaceand of the toner image) or can be transferred to another surface, towhich it then can be similarly fixed.

A number of requirements are implicit in such development schemes.Namely, the electrostatic attraction between the toner and carrierparticles must be strong enough to keep the toner particles held to thesurfaces of the carrier particles while the developer is beingtransported to and brought into contact with the latent image, but whenthat contact occurs, the electrostatic attraction between the tonerparticles and the latent image must be even stronger, so that the tonerparticles are thereby pulled away from the carrier particles anddeposited on the latent image-bearing surface. In order to meet theserequirements for proper development, the level of electrostatic chargeon the toenr particles should be maintained within an adequate range.

Many well-known types of toner particles useful in dry developerscomprise polyester binder materials, chosen for their good combinationsof advantageous properties, such as toughness, transparency, goodadhesion to substrates, and fusing characteristics, such as the abilityto be fixed to paper at relatively low fusing temperatures while notpermanently adhering to fusing rolls, except at relatively hightemperatures. As used herein, the term, "polyester", is intended to meana polymer in which backbone recurring units are connected by esterlinkages. As is well known, polyesters useful as binder mateirals intoner particles can be linear, branched, or lightly crosslinked and canbe fashioned from any of many different monomers, typically bypolycondensation of monomers containing two or more carboxylic acidgroups (or derivatives thereof, such as anhydride or ester groups) withmonomers containing two or more hydroxyl groups.

Also, toner particles in dry developers often contain material referredto as a charge agent or charge-control agent, which helps to establishand maintain toner charge within an acceptable range. Many types ofcharge-control agents have been used and are described in the publishedpatent literature.

One general type of charge-control agent known to be useful in polyestertoner particles for dry developers comprises a quaternary phosphoniumsalt. A number of such quaternary phosphonium salt charge-control agentsare described, for example, in U.S. Pat. Nos. 4,496,643 and 4,537,848.Unfortunately, many of those known charge-control agents can exhibit anumber of drawbacks in some developers.

For example, some of the known quaternary phosphonium salt charge agentslack thermal stability and, thus, totally or partially decompose duringattempts to mix them with known toner binder materials in well-knownprocesses of preparing toners by mixing addenda with molten tonerbinders. Such processes are often referred to as melt-blending ormelt-compounding processes and are commonly carried out at elevatedtemperatures. Thus, charge agents that are thermally unstable attemperatures encountered during melt-compounding can exhibit thisdecomposition problem.

Also, some of the known quaternary phosphonium salt charge-controlagents have relatively high melting points. During melt-blending, amolten charge agent can be more quickly, efficiently, and uniformlydispersed in the molten toner binder than can a solid charge agent.Non-uniform dispersion can result in poor or inconsistent charge-controlperformance from toner particle to toner particle (among otherundesirable effects discussed below). Therefore, it is a drawback tohave a charge agent that will not become molten at the temperatures thatwill be encountered in melt-compounding, because such a charge agentwill be slowly, inefficiently, and non-uniformly dispersed in the tonerbinder during some melt-blending processes.

Furthermore, some of the known quaternary phosphonium salt charge agentshave relatively high electrical conductivity, which can lead to poorperformance of some developers.

Also, some known quaternary phosphonium salt charge agents exhibit highsensitivity to changes in environmental relative humidity and/ortemperature, which can lead to erratic performance of the charge agentsunder changing environmental conditions.

Additionally, some of the known quaternary phosphonium salt chargeagents will adversely interact chemically and/or physically with otherdeveloper or copier components. For example, some will interact withcarrier or carrier coating materials (e.g., fluorohydrocarbon polymercoatings such as poly-(vinylidene fluoride)) and lead to prematurecarrier aging and shortened useful developer life. Some will interactwith certain toner colorants to cause unacceptable hue shifts in thetoner. Some will interact with copier fuser rollers (e.g., rollerscoated with fluorohydrocarbon polymers such as poly(vinylidenefluoride-co-hexafluoropropylene)) to cause premature failure of thecopier's toner fusing system. Some will interact with surface layers ofelectrostatographic elements to cause poor latent image formation andshortened useful element life.

Also, poor dispersibility of some of the known quaternary ammonium saltcharge agents in some of the known polyester toner binder materials,either because the charge agent remains solid during melt-compounding(as discussed above) or undergoes phase separation from the toner binderwhen it is attempted to increase its concentration therein, or becauseit is incompatible with or otherwise poorly dispersible in the binder,can lead to worsening of some of the problems mentioned above.Non-uniform dispersion of charge agent means that higher concentrationsor agglomerations of charge agent will exist in some portions of thetoner binder mix, compared to others. In typical melt-blendingprocesses, the toner mixture is cooled and ground down to desiredparticle size after melt-blending. Agglomerations of charge agentprovide sites in the mixture where fracture is more likely to occurduring grinding. The new surfaces created by such fracture will have ahigher concentration of charge agent than will internal sites. Thus, thefinal toner particles will have a higher surface concentration of chargeagent than internal concentration. It should be readily appreciated thatif a charge agent tends to adversely interact with the environment,copier components, or other developer components, higher surfaceconcentrations of charge agent on the toner particles will lead to agreater degree of such interaction, thus exacerbating problems such ashigh conductivity, high environmental sensitivity, and premature failureof carrier and copier component materials.

Furthermore, in the known dry developers containing known quaternaryphosphonium salt charge-control agents in toner particles, thecharge-control agents are not chemically bonded to the other tonercomponents, e.g., the polymeric binders. Therefore, the charge-controlagents can migrate within, and exude from, the toner particles overtime, causing non-uniform dispersion, inconsistent and changing tonercharge, and worsening of adverse interactions noted above.

Also, many of the known quaternary phosphonium salt charge-controlagents are not as efficient at creating the desired charge level as isdesirable; i.e., it requires a relatively high concentration of thecharge-control agent to produce the desired charge level. The greaterthe concentration of charge-control agent required, the greater wil bethe change of phase separation and non-uniform dispersion, the greaterwill be the chance of adverse interactions and poor or inconsistentcharging, and the greater will be the cost of the charge-control agentrequired per unit amount of toner.

Additionally, with many of the known quaternary phosphonium saltcharge-control agents, the ability to produce changes in charge level byincreasing charge-control agent concentration, falls off relativelyquickly, i.e., a plateau of charge level versus concentration isreached, and this may occur before the charge reaches the desired level.In that case, no matter how much more the concentration ofcharge-control agent is increased, the desired charge level will neverbe achieved.

It would, therefore, be desirable to provide new polyester tonerparticles containing quaternary phosphonium salt compositions thatperform the charge-controlling function well therein, while avoiding orminimizing all of the drawbacks noted above. The present invention doesthis.

SUMMARY OF THE INVENTION

The invention provides an electrostatographic toner particle having anaverage diameter in the range of 0.01 to 100 micrometers and comprisinga binder polyester and a charge-control agent comprising a quaternaryphosphonium salt, wherein the phosphonium salt has a cationic portioncomprising a phosphorus atom covalently bonded to at least one moietycontaining an ester linkage to the binder polyester.

The phosphonium polyesters serve as dual function binder/charge-controlagents in the inventive electrostatographic toner particles and have anumber of advantages over the combinations of polyester binders andquaternary phosphonium salt charge-control agents described in the priorart.

The polyesters in the inventive toner particles have good thermalstability. Neither the polyesters as a whole, nor their quaternaryphosphonium salt portions will thermally decompose during processes ofmelt-blending them with other addenda which it may be desirable toinclude in toner particles (e.g., other binders, colorants, releaseagents, etc.). They do not exhibit unacceptably high conductivity orenvironmental sensitivity.

In the inventive toner particles, the polyesters have not been found tointeract unacceptably with commonly utilized toner colorants, carriermaterials, or copier components such as fuser rolls andelectrophotographic elements.

When such a polyester is used as the sole binder/charge-control agent ina toner particle of the invention, there is, of course, no problem oflack of compatibility with other binders. When it is desired toadditionally include another binder polyester in the inventive tonerparticle, both polyesters can easily be fashioned to provide goodcompatibility with each other (most easily by choosing some of therecurring units of both polyesters to be the same or similar or bychoosing recurring units that are already known to provide goodcompatibility when included in polyesters intended to be blendedtogether). Since the quarternary phosphonium salt charge-control moietyis covalently bonded to the polyester, there is no problem ofdispersibility, and no such problems have been found to arise when thepolyester is mixed with another compatible polyester binder, inpreparing toner particles of the invention.

Also because the phosphonium moiety is covalently bonded to thepolyester, there is no migration within, or exuding of thecharge-control moiety from, the inventive toner composition.

Furthermore, it has been unexpectedly found that the covalent bonding ofthe cationic portion of the phosphonium salt to the polyester providesnot only a good charge-control material, but one that is significantlymore efficient (i.e., provides the desired charge level at a much lowerconcentration of the phosphonium salt moiety) than the correspondingnon-bonded mixtures of polyesters and non-polymeric quaternaryphosphonium salt charge-control agents in toner particles of the priorart or than corresponding polyesters wherein only the anionic portion ofthe phosphonium salt is covalently bonded to the polyester. Also, thereis, therefore, less chance of mixing problems or adverse interactions.

Along with their greater charge-control efficiency, the polyestersuseful in the inventive toner particles are also more capable ofachieving desired charge levels than the corresponding non-polymericphosphonium charge agents; i.e., greater changes in charge level areachievable by increasing the phosphonium salt moiety concentration thanare possible with the non-polymeric phosphonium charge agents, whichtend to plateau at a lesser change in charge level. Also, if desired,greater concentrations of the polyester-bound phosphonium saltcharge-control moiety can be included in toner particles of theinvention than with the prior art non-polymeric salts, since there is noproblem of phase separation at higher concentrations.

An additional advantageous feature of some embodiments of the new tonerparticles is that the polyesters included therein can be prepared byknown melt-polycondensation techniques, rather than having to use morecomplex solution-polycondensation techniques wherein additional stepsmust be taken to isolate the polyester from solvents. This is becausethe monomers (including the phosphonium salt-containing monomers) neededto produce the polyesters are capable of experiencing the relativelyharsh thermal environment (e.g., 220°-240° C.) of melt-phase synthesisfor necessarily prolonged periods (e.g., up to 5 or 6 hours) withoutundergoing thermal degradation.

The invention also provides a new dry electrostatographic developercomprising the inventive toner particles mixed with carrier particles.

It should be noted that other inventive toners and developers containingother phosphonium polyesters or other phosphonium polymers, aredescribed and claimed in copending U.S. Pat. applications Ser. Nos.229,045; 229,046; and 229,047, all filed Aug. 5, 1988. Also, some of thepolyesters useful in the toner particles of the present invention areconsidered to be inventive as polyester per se and are described andclaimed in copending U.S. Pat. application Ser. No. 229,044, also filedAug. 5, 1988.

DESCRIPTION OF PREFERRED EMBODIMENTS

A polyester useful in a toner particle of this invention comprises anyof the recurring units known to be useful in polyester toner binders ingeneral, with the additional proviso that the polyester contains aquarternary phosphonium salt comprising a cationic portion and ananionic portion, wherein the cationic portion of the salt comprises aphosphorous atom covalently bonded to at least one moiety containing anester linkage to the rest of the polyester.

While the cationic phosphonium moiety is monovalently bonded to the restof the polyester through one ester linkage in some toner embodiments (asan endcapping unit or pendant unit), in other embodiments it isdivalently incorporated into the backbone of the polyester as arecurring backbone unit (either through two ester linkages which arecontained in one moiety to which a cationic phosphonium atom iscovalently bonded or through two ester linkages, which are contained intwo separate moieties to which a cationic phosphonium atom is covalentlybonded), and in still other embodiments the cationic phosphonium moietyis trivalently bonded into the polyester through three ester linkages toform a recurring backbone unit that also serves as a branching orcrosslinking site.

Also, in addition to being ionically bonded to the cationic phosphoniumportion to form the phosphonium salt, the anionic portion of the saltcan optionally also be covalently bonded to the rest of the polyester,either monovalently or divalently, through one or more ester linkages.

In all of the toner embodiments mentioned above the polyester has thesuperior charge-control capabilities previously described, apparentlybecause of the covalent bonding of the cationic portion of thephosphonium salt to the rest of the polyester.

In some preferred embodiments of the inventive toner particle thephosphonium salt has the structure ##STR1## or the structure ##STR2##wherein:

R¹, R², R³, and R⁴ are each independently: alkyl which is unsubstituted,substituted with one or more aryl, or substituted with one or more groupcontaining an ester linkage to the binder polyester; or aryl which isunsubstituted, substituted with one or more alkyl, or substituted withone or more group containing an ester linkage to the binder polyester;

R⁵ is alkylene, oxydialkylene, or arylenedialkylene; and

A.sup.⊖ is an anion;

with the provisos that:

each alkyl or alkylene moiety recited above has from 1 to 20 carbonatoms;

each aryl or arylene moiety recited above has from 6 to 14 carbon atoms;and

at least one of R¹, R², R³, and R⁴ contains at least one ester linkageto the binder polyester.

In some even more preferred embodiments of the inventive toner particle,wherein the phosphonium polyesters and the monomers useful to preparethem have the thermal stability to withstand the harsh thermalconditions of melt-polycondensation, the toner particle comprises aphosphonium polyester, wherein the phosphonium salt is of structure I orII above, wherein R¹, R², R³, and R⁴ are each independently alkyl whichis unsubstituted or substituted with one or more aryl; or aryl which isunsubstituted, substituted with one or more alkyl, or substituted withone or more group containing an ester linkage to the binder polyester;and wherein A.sup.⊖ has the structure

    .sup.⊖ O.sub.3 S--R.sup.6

wherein

R⁶ is aryl which is unsubstituted or substituted with one or more alkyl,halide, or group containing an ester linkage to the binder polyester;

R⁵ is alkylene, oxydialkylene, or arylenedialkylene;

each alkyl or alkylene moiety recited above has from 1 to 20 carbonatoms;

each aryl or arylene moiety recited above has from 6 to 14 carbon atoms;and

at least one of R¹, R², R³, and R⁴ contains at least one ester linkageto the binder polyester.

Such phosphonium polyesters can be prepared by any of the knownpolycondensation techniques for producing polyesters, e.g., solutionpolycondensation or melt-phase polycondensation. Melt-polycondensationis the preferred technique, because it requires no isolation of productfrom solvents.

Monomers useful to prepare polyesters for the toner particles of theinvention contain groups functional to produce ester linkages, e.g.,carboxylic acid, ester, anhydride, hydroxy, epoxide, etc. Monomersuseful to prepare backbone recurring units contain two or more suchgroups, while monomers intended to form endcaps or pendant units cancontain just one. The quaternary phosphonium salts are most convenientlyincorporated in the form of monomers of these types during thepolycondensation, but they can also be appended to functionalized sitesafter polymerization if desired.

Other than the phosphonium salt-containing monomers needed, othermonomers useful in preparing phosphonium polyesters for the inventivetoner particles are any of those known to be useful in general toprepare polyester binders for toner particles. Some specific examples ofsuch monomers are: 1,4-cyclohexanediol; 1,4-cyclohexanedimethanol;1,4-cyclohexanediethanol; 1,4-bis(2-hydroxyethoxy)cyclohexane;1,4-benzenedimethanol; 1,4-benzenediethanol; norbornylene glycol;decahydro-2,6-naphthalenedimethanol; glycerol; bisphenol A; ethyleneglycol; diethylene glycol; triethylene glycol; 1,2-propanediol;1,3-propanediol; 1,4-butanediol; 2,3-butanediol; 1,5-pentanediol;neopentyl glycol; 1,6-hexanediol; 1,7-heptanediol; 1,8-octanediol;1,9-nonanediol; 1,10-decanediol; 1,12-dodecanediol; pentaerythritol;2,2,4-trimethyl-1,6-hexanediol; 4-oxa-2,6-heptanediol;1,4-bis(2-hydroxyethoxy)cyclohexane; 2,2-dimethyl-1,3-dihydroxypropane;succinic acid; sebacic acid; 2-methyladipic acid; diglycolic acid;thiodiglycolic acid; fumaric acid; cyclohexane-1,3-dicarboxylic acid;cyclohexane-1,4-dicarboxylic acid; cyclopentane-1,3-dicarboxylic acid;2,5-norbornanedicarboxylic acid; phthalic acid; isophthalic acid;terephthalic acid; 2-butylisophthalic acid; 2,6-naphthalenedicarboyxlicacid; 1,4-naphthalenedicarboxylic acid; 1,5-naphthalenedicarboxylicacid; 4,4'-sulfonyldibenzoic acid; 4,4'-oxydibenzoic acid;binaphthyldicarboxylic acid; 9,10-triptycenedicarboxylic acid; and theanhydrides and lower alkyl esters of the acids mentioned.

Some specific examples of phosphonium salt-containing monomers useful inpreparing the phosphonium polyesters useful in the inventive tonerparticles are: methylphenylbis(4-carbomethoxyphenyl)phosphonium3,5-bis(carbomethoxy)benzenesulfonate;

4-carbomethoxyphenylmethyldiphenylphosphonium3,5-bis(carbomethoxy)benzenesulfonate;

4-carbomethoxyphenylmethyldiphenylphosphonium p-toluenesulfonate;

methylbis(4-carbomethoxyphenyl)phenylphosphonium p-toluenesulfonate;

methylbis(4-acetoxyphenyl)phenylphosphonium p-toluenesulfonate;

methylbis(4-hydroxyphenyl)phenylphosphonium p-toluenesulfonate;

4-acetoxyphenylmethyldiphenylphosphonium p-toluenesulfonate;

methyltris(4-acetoxyphenyl)phosphonium p-toluenesulfonate;

methylbis(4-carbomethoxyphenyl)phenylphosphonium tetraphenylborate;

4-carbomethoxybenzyltriphenylphosphonium p-toluenesulfonate;

4-carbomethoxybenzyltriphenylphosphonium3,5-bis(carbomethoxy)benzenesulfonate;

3-carbomethoxybenzyltriphenylphosphonium p-toluenesulfonate;

3-carbomethoxybenzyltriphenylphosphonium3,5-bis(carbomethoxy)benzenesulfonate;

3,4-dicarbomethoxybenzyltriphenylphosphonium p-toluenesulfonate;

methylbis(3-hydroxypropyl)phenylphosphonium p-toluenesulfonate;

benzylbis(4-acetoxyphenyl)phenylphosphonium bromide;

ethylenebis(carbomethoxymethyldiphenylphosphonium) dibromide;

ethylenebis(4-hydroxyphenyldiphenylphosphonium) di-p-toluenesulfonate;

methyltris(4-carbomethoxyphenyl)phosphonium p-toluenesulfonate;

ethylenebis(4-carbomethoxyphenyldiphenylphosphonium)di-p-toluenesulfonate;

oxydiethylenebis(4-acetoxyphenyldiphenylphosphonium)di-p-toluenesulfonate;

ethylenebis(4-acetoxyphenyldiphenylphosphonium) di-p-toluenesulfonate;

3,5-dicarbomethoxyphenylmethyldiphenylphosphonium p-toluenesulfonate;and

xylylenebis(4-acetoxyphenyldiphenylphosphonium) di-p-toluenesulfonate.

Useful functionalized quaternary phosphonium salt-containing monomers(i.e., those containing the groups necessary to form ester linkages) areprepared by well-known methods of either reacting appropriatefunctionalized tertiary phosphines with appropriate alkylating agents(e.g., the arylsulfonates) or reacting functionalized alkylating agentswith tertiary phosphines, preferably the former. The bisphosphoniumsalts are readily obtained by using alkylating agents having tworeactive sites. If the alkylating agents employed are halides, thephosphonium halide is readily converted into the phosphoniumarylsulfonate by ion exchange with the sodium or silver salt of theappropriate arylsulfonic acid. Any desired functionalized tertiaryphosphines not readily available can be prepared by known methodsdescribed in the general literature.

Further details of preparation of monomers and polyesters for some ofthe preferred embodiments are included in the Preparations and Examplesbelow.

Preferred polyesters for use as dual function binder/charge-controlagents in preferred electrostatographic toner particles of the inventionare amorphous polyesters having a glass transition temperature (referredto as Tg) in the range of about 40° to about 150° C., and morepreferably about 50° to about 120° C. Such polyesters can be heat-fixedto smooth-surfaced film substrates as well as to more conventionalsubstrates, such as paper, without difficulty. Tg can be determined byany conventional method, e.g., differential scanning calorimetry.

Preferred embodiments contain polyesters having inherent viscosity inthe range of about 0.01 to about 0.65 deciliters per gram (dl/g), asmeasured at 25° C. and at a concentration of 2.5 g/l in a solution ofdichloromethane (DCM), dimethylformamide (DMF), or a 1:1 by weight mixof phenol:chlorobenzene (P:CB).

To perform the charge-control function in an inventiveelectrostatographic toner particle, the phosphonium polyester willusually be included in the toner particle in an amount sufficient toyield a concentration of individual phosphonium salt portions of thepolyester in the range of about 10⁻⁹ to about 10⁻⁴ moles of phosphoniumsalt moieties per gram of all material in the toner particle. The exactconcentration employed will depend on the level of charge desired andthe triboelectric nature of the polyester and all other materials in theinventive toner particle (and also the triboelectric nature of thecarrier particles, if the toner particles are intended to be mixed withcarrier particles to form an inventive so-called "two-component"electrostatographic developer). The polyesters can also be used asbinder/charge-control agents in toner particles intended to be used bythemselves (i.e., with no carrier particles) as a so-called "singlecomponent" electrostatographic developer.

It should be appreciated that the desired concentration of phosphoniumsalt moieties in the inventive toner particle can be effected in morethan one manner. In cases where the toner particle consists of only thephosphonium polyester, the moles of phosphonium salt moieties per gramof toner particle will be equal to the moles of phosphoniumsalt-containing units per gram of polyester. In cases where othermaterials (e.g., other binders, colorants, release agents, etc.) areadditionally included in the inventive toner particle, the moles ofphosphonium salt-containing units per gram of polyester must be higherthan the moles of phosphonium salt moieties per gram of toner particleto compensate for the additional weight of other materials in theparticle. Thus, phosphonium polyesters useful in the inventive tonerparticles, include not only those in which phosphonium salt-containingunits are included in a concentration range of 10⁻⁹ to 10⁻⁴ moles pergram of polyester, but also others in which the concentration ofphosphonium salt-containing units is considerably higher than thatrange.

As noted above, the inventive toner particles can additionally containother materials, such as other binders, colorants, release agents, etc.

Other binders which can be mixed with the cation-bound phosphoniumpolyesters in inventive toner particles include any of the polymersknown to be useful as toner binders and also other polyesters containingquaternary phosphonium salts, wherein only the anionic portion of thesalt is covalently bonded to the polyester through an ester linkage.These other polyesters generally provide charge levels lower than thecation-bound phosphonium polyesters at a given concentration ofphosphonium salt moieties, but they can be useful to downwardly adjustthe charge level provided by the cation-bound phosphonium polyesterswhen mixed therewith, if desired.

Among the various other polymeric binders which can be mixed with thephosphonium polyesters in toner particles of the invention are otherpolyesters (including polycarbonates), polyamides, phenol-formaldehydepolymers, polyesteramides, alkyd resins, and vinyl-addition polymers andcopolymers, typically formed from monomers such as styrenes, butadiene,acrylates and methacrylates, among others. For further descriptions ofsome of these other polymeric binders, see, for example, U.S. Pat. Nos.3,809,554; Re 31,072; 3,694,359; 2,917,460; 2,788,288; 2,638,416;2,618,552; 4,416,965; 4,691,966; and 2,659,670.

Numerous colorant materials selected from dyestuffs or pigments can beemployed in toner particles of the invention. Such materials serve tocolor the toner and/or render it more visible. Of course, suitable tonermaterials having the appropriate charging characteristics can beprepared without the use of a colorant material where it is desired tohave a developed image of low optical density. In those instances whereit is desired to utilize a colorant, the colorants can, in principle, beselected from virtually any of the compounds mentioned in the ColourIndex Volumes 1 and 2, Second Edition.

Included among the vast number of useful colorants are such materials asHansa Yellow G (C.I. 11680), Nigrosine Spirit soluble (C.I. 50415),Chromogen Black ETOO (C.I. 45170), solvent Black 3 (C.I. 26150),Fuchsine N (C.I. 42510), C.I. Basic Blue 9 (C.I. 52015). Carbon blackalso provides a useful colorant. The amount of colorant added may varyover a wide range, for example, from about 1 to about 20 percent of theweight of the polymer. Particularly good results are obtained when theamount is from about 1 to about 10 percent.

To be utilized as a binder/charge-control agent in the inventiveelectrostatographic toners, the phosphonium polyester is mixed in anyconvenient manner (preferably by melt-blending as described, forexample, in U.S. Pat. Nos. 4,684,596 and 4,394,430) with any otherdesired addenda, and the mix is then ground to desired size to form afree-flowing powder of inventive toner particles containing thepolyester.

Toner particles of the invention have an average diameter between about0.01 μm and about 100 μm, a value in the range from about 1.0 to about30 μm being preferable for many currently used machines. However, largeror smaller particles may be needed for particular methods of developmentor development conditions.

To be utilized as toners in electrostatographic developers of theinvention, toner particles of this invention can be mixed with a carriervehicle. The carrier vehicles which can be used to form such inventivedeveloper compositions can be selected from various materials. Suchmaterials include carrier core particles and core particles overcoatedwith a thin layer of film-forming resin.

The carrier core materials can comprise conductive, non-conductive,magnetic, or non-magnetic materials. For example, carrier cores cancomprise glass beads; crystals of inorganic salts such as aluminumpotassium chloride; other salts such as ammonium chloride or sodiumnitrate; granular zircon; granular silicon; silicon dioxide; hard resinparticles such as poly(methyl methacrylate); metallic materials such asiron, steel, nickel, carborundum, cobalt, oxidized iron; or mixtures oralloys of any of the foregoing. See, for example, U.S. Pat. Nos.3,850,663 and 3,970,571. Especially useful in magnetic brush developmentschemes are iron particles such as porous iron particles having oxidizedsurfaces, steel particles, and other "hard" or "soft" ferromagneticmaterials such as gamma ferric oxides or ferrites, such as ferrites ofbarium, strontium, lead, magnesium, or aluminum. See, for example, U.S.Pat. Nos. 4,042,518; 4,478,925; and 4,546,060.

As noted above, the carrier particles can be overcoated with a thinlayer of a film-forming resin for the purpose of establishing thecorrect tribo-electric relationship and charge level with the toneremployed. Examples of suitable resins are the polymers described in U.S.Pat. Nos. 3,547,822; 3,632,512; 3,795,618 and 3,898,170 and BelgianPatent No. 797,132. Other useful resins are fluorocarbons such aspolytetrafluoroethylene, poly(vinylidene fluoride), mixtures of these,and copolymers of vinylidene fluoride and tetrafluoroethylene. See, forexample, U.S. Pat. Nos. 4,545,060; 4,478,925; 4,076,857; and 3,970,571.such polymeric fluorohydrocarbon carrier coatings can serve a number ofknown purposes. One such purpose can be to aid the inventive developerto meet the electrostatic force requirements mentioned above by shiftingthe carrier particles to a position in the triboelectric seriesdifferent from that of the uncoated carrier core material, in order toadjust the degree of triboelectric charging of both the carrier andtoner particles. Another purpose can be to reduce the frictionalcharacteristics of the carrier particles in order to improve developerflow properties. Still another purpose can be to reduce the surfacehardness of the carrier particles so that they are less likely to breakapart during use and less likely to abrade surfaces (e.g.,photoconductive element surfaces) that they contact during use. Yetanother purpose can be to reduce the tendency of toner material or otherdeveloper additives to become undesirably permanently adhered to carriersurfaces during developer use (often referred to as scumming). A furtherpurpose can be to alter the electrical resistance of the carrierparticles.

A typical developer composition of the invention containing inventivetoner particles and a carrier vehicle generally comprises from about 1to about 20 percent by weight of the toner particles and from about 80to about 99 percent by weight carrier particles. Usually, the carrierparticles are larger than the toner particles. Conventional carrierparticles have a particle size on the order of from about 20 to about1200 microns, preferably 30-300 microns.

Alternatively, toners of the present invention can be used in a singlecomponent developer, i.e., with no carrier particles.

Toner and developer compositions of this invention can be used in avariety of ways to develop electrostatic charge patterns or latentimages. Such developable charge patterns can be prepared by a number ofmeans and be carried for example, on a light sensitive photoconductiveelement or a non-light-sensitive dielectric-surfaced element such as aninsulator-coated conductive sheet. One suitable development techniqueinvolves cascading the developer composition across the electrostaticcharge pattern, while another technique involves applying tonerparticles from a magnetic brush. This latter technique involves the useof a magnetically attractable carrier vehicle in forming the developercomposition. After imagewise deposition of the toner particles, theimage can be fixed, e.g., by heating the toner to cause it to fuse tothe substrate carrying the toner. If desired, the unfused image can betransferred to a receiver such as a blank sheet of copy paper and thenfused to form a permanent image.

The following preparations and examples are presented to furtherillustrate the preparation and performance of some preferred embodimentsof the toners and developers of the invention and the polyestersemployed therein and to compare their properties and performance tothose of toners and developers outside the scope of the invention.

In the preparations and examples below polyester names contain anindication of the molar ratios of the various units in the polyester. Insome preparations and examples (as indicated therein) the relativeconcentrations of units are expressed as molar ratios of the monomersused to prepare the polyester.

Where toner charge in a developer is indicated, usually as microcoulombsper gram of toner particles (μc/g), the charge was sometimes determinedby plating the toner by electrical bias from a magnetic brush of thedeveloper onto the electrically insulating layer of a test element. Thiselement was composed of, in sequence, a film support, an electricallyconducting layer and the insulating layer. The amount of plating wasusually controlled to produce a mid-range reflection optical density(OD). For purposes of the present invention, toner containing colorantwas plated to an OD of about 0.3. The test element containing the platedtoner was connected via the conducting layer to an electrometer. Theplated toner was then rapidly removed in a current of forced air,causing a flow of current to register in the electrometer as a charge,in microcoulombs. The registered charge was divided by the weight of theplated toner to obtain the charge per mass of toner. Thischarge-measurement method is referred to as the "Blowoff" method.

In some cases toner charge was measured by a technique referred to asthe "MECCA" method, wherein the apparatus consists of two parallel metalplates separated by insulating posts about 1 cm high. An ACelectromagnet is located beneath the lower plate to provide magneticagitation, while a DC electric potential of about 2000 volts can beapplied across the plates. A sample of about 0.1 gram of developer isweighed, placed on the lower plate, and charged by magnetic agitationfor 30 seconds. Next, both the electric and magnetic fields are appliedfor 30 seconds. The toner is separated from the carrier by the combinedagitation and electric field and is transported to the upper plate bythe electric field. The charge on the toner collected by the top plateis measured in microcoulombs by an electrometer, and the weight of toneris determined. Charge is reported as microcoulombs per gram of toner(μc/g).

PREPARATION 1 3,5-Dimethylphenyldiphenylphosphine

In a 3-neck 1 liter flask equipped with blade stirrer, nitrogen inlet,Claissen adaptor, condenser, drying tube and constant pressure droppingfunnel, was placed 6.67 g (0.274 g atoms) of magnesium turnings. Under anitrogen flow, the glassware was dried with heating via a heat gun. Tothe magnesium was added a portion of a solution of 55.5 g (0.30 mol) of5-bromo-m-xylene in 150 ml dry THF (tetrahydrofuran). Reaction wasinitiated with external heating and the balance of the solution wasadded dropwise over approximately 30 min, maintaining gentle reflux. themixture was then stirred for another 1 hr after which a solution of 41.3g (0.188 mol) of chlorodiphenyl-phosphine in 150 ml of dry THF was addedover approximately 10 min. The mixture was then heated at reflux for 2hr, cooled and poured into ice. The mixture was neutralized withconcentrated HCl and nitrogen was bubbled through the mixture overnight.The organic layer was taken up in methylene chloride and separated fromthe aqueous layer. Concentrating the organic layer afforded an oil whichcrystallized on standing. After triturating with an equal volume ofmethanol, the solid was collected and recrystallized from methanol. Theyield of 3,5-dimethylphenyldiphenylphosphine was 37.5 g (68.7% oftheory); mp=67°-9° C.

Anal. Calcd. for C₂ H₁₉ P: C, 82.7; H, 6.6: P, 10.7.

Found: C, 83.2; H, 6.7; P, 10.7.

PREPARATION 2 3,5-Dicarboxyphenyldiphenylphosphine Oxide

To a mixture of 30.0 g (0.1033 mol) of3,5-dimethylphenyldiphenylphosphine (from Preparation 1), 125 ml ofpyridine and 75 ml of water heated on a steam bath was added 233.9 g(1.48 mol) of potassium permanganate portionwise. After completion ofaddition, the mixture was stirred for another 1.5 hr and cooled.Methanol (100 ml) was added and the mixture was stirred for 15 min. Themixture was filtered and the manganese dioxide was washed with water.the combined filtrate and wash was acidified with concentratedhydrochloric acid and the solid precipitate was collected, washed withwater and dried. The yield of 3,5-dicarboxyphenyldiphenyl-phosphineoxide was 22.7 g (60.0% of theory); mp=283°-6° C.

Anal. Calcd. for C₂₀ H₁₅ PO₅ : C, 65.6; H, 4.1; O, 21.8; P, 8.5.

Found: C, 65.6; H, 4.2; O, 21.6; P, 8.6. Structure confirmed by NMR.

PREPARATION 3 3,5-Dicarbomethoxyphenyldiphenylphosphine Oxide

A mixture of 20.0 g (5.46×⁻² mol) of3,5-dicarboxyphenyldiphenylphosphine oxide (from Preparation 2), 134 mlof methanol and 1.5 ml of concentrated H₂ SO₄ was heated at reflux for18 hr and cooled. The solution was then poured into dilute sodiumbicarbonate to give a white precipitate which was collected, washed withwater and dried. The yield of 3,5-dicarbomethoxyphenyldiphenylphosphineoxide was 18.9 g (87.8% of theory); mp=170°-1° C.

Anal. Calcd. for C₂₂ H₁₉ O₅ P: C, 67.0; H, 4.9; P, 7.9.

Found: C, 67.0; H, 4.8; P, 7.9.

Structure confirmed by NMR.

PREPARATION 4 3,5-Dicarbomethoxyphenyldiphenylphosphine

To a mixture of 17.0 g (4.31×10⁻² mol) of3,5-dicarbomethoxyphenyldiphenylphosphine oxide (from Preparation 3),4.71 g (4.65×10⁻² mol) of triethylamine and 196 ml of dry toluene undernitrogen was added 6.76 g (4.74×10⁻² mol) of trichlorosilane. Themixture was then heated at reflux for 15.25 hr and cooled. A solution of20% sodium hydroxide (49 ml) was added and the mixture was stirred. Theorganic layer was separated, washed with two 250 ml portions of water,dried over MgSO₄ and concentrated to an oil which crystallized. Thesolid was recrystallized twice from methanol and dried. The yield of3,5-dicarbomethoxyphenyldiphenylphosphine was 14.0 g (85.8% of theory);mp=103-4.5° C.

Anal. Calcd. for C₂₂ H₁₉ O₄ P: C, 69.8; H, 5.1; O, 16.9; P, 8.2.

Found: C, 71.0; H, 5.2; O, 16.8; P, 8.0.

Structure confirmed by NMR.

PREPARATION 5 Methyl[3,5-bis(carbomethoxy)phenyl]diphenylphosphoniump-toluenesulfonate

A mixture of 9.46 g (2.5×10⁻² mol) of3,5-dicarbomethoxyphenyldiphenylphosphine (from Preparation 4), and 4.66g (2.5×10³¹ 2 mol) of methyl p-toluenesulfonate was heated in a 130° C.bath with nitrogen bubbling through the melt for two hours. Theresultant product was cooled to an amorphous glass.

Anal. Calcd. for C₃₀ H₂₉ O₇ PS: C, 63.8; H, 5.2; P, 5.5; S, 5.7.

Found: C, 62.7; H, 5.1; P, 5.5; S, 5.9.

Structure confirmed by NMR.

PREPARATION 6 Bis(4-acetoxyphenyl)phenylphosphine

A mixture of 18.76 g (0.05 mol) of bis(4-hydroxyphenyl)phenylphosphinehydrobromide, 9.1 g (0.11 mol) of sodium acetate and 61 ml of aceticanhydride was heated at reflux for 4 hr and cooled. The mixture waspoured onto a mixture of ice and water and the resultant solid wascollected and recrystallized from methanol. The yield ofbis(4-acetoxyphenyl)phenylphosphine was 4.9 g (25.9% of theory);mp=118°-20° C.

Anal. Calcd. for C₂₂ H₁₉ O₄ P: C, 69.8; H, 5.1; P, 8.2.

Found: C, 70.0; H, 5.2; P, 7.9.

Structure confirmed by NMR.

PREPARATION 7 Methylbis(4-acetoxyphenyl)phenylphosphoniump-toluenesulfonate

A mixture of 37.8 g (0.10 mol) of bis(4-acetoxyphenyl)phenylphosphine(from Preparation 6) and 18.6 g (0.10 mol) of methyl p-toluenesulfonatewas heated with stirring under nitrogen in a 125°-135° C. oil bath forone hour. The resultant syrup was then cooled to an amorphous glass. Theyield of methylbis(4-acetoxyphenyl)phenylphosphonium p-toluenesulfonatewas 55.1 g (97.6% of theory).

Anal. Calcd. for C₃₀ H₂₉ O₇ PS: C, 63.8; H, 5.2; P, 5.5; S, 5.7.

Found: C, 63.5; H, 5.3; P, 5.3; S, 5.6.

Structure confirmed by NMR.

PREPARATION 8 1,4-Xylylenebis(4-acetoxyphenyldiphenylphosphonium)Di-p-toluenesulfonate

A solution of 4.8 g (17.24×10⁻³ mol) of silver p-toluenesulfonate in 50ml of 1:1 methanol: H₂ O was added to a solution of 7.8 g (8.62×10⁻³mol) of 1,4-xylylenebis(4-acetoxyphenyldiphenyl-phosphonium) dibromide.A greenish-white precipitate formed immediately. After stirring foranother 5 min, the mixture was filtered and the filtrate wasconcentrated to a glassy residue. The glass was washed with ether anddried. The yield of 1,4-xylylenebis(4-acetoxyphenyldiphenylphosphonium)di-p-toluenesulfonate was 7.5 g (80.0% of theory).

Anal. Calcd. for C₆₂ H₅₆ O₁₀ P₂ S₂ : C, 68.5; H, 5.2; P, 5.7; S, 5.9.

Found: C, 67.5; H, 5.2; P, 5.4; S, 6.0

Structure confirmed by NMR.

PREPARATION 9 Ethylenebis(4-carbomethoxyphenyldiphenylphosphonium)di-p-toluenesulfonate

A mixture of 3.20 g (0.01 mol) of(4-carbomethoxyphenyl)diphenylphosphine and 1.85 g (0.005 mol) of1,2-bis(p-toluenesulfonyloxy)ethane was heated in a 130° C. bath wirhstirring for 12.75 hr and cooled to an amorphous glass.

Anal. Calcd. for C₅₆ H₅₂ O₁₀ P₂ S₂ : C, 66.5; H, 5.2; P, 6.1; S, 6.3.

Found: C, 66.2; H, 5.2; P, 6.0; S, 6.7.

Structure confirmed by NMR.

PREPARATION 10 Bis(p-carbomethoxyphenyl)phenylmethylphosphoniump-toluenesulfonate

A mixture of 18.92 g (0.05 mol) ofbis(p-carbomethoxyphenyl)phenylphosphine and 9.31 g (0.05 mol) of methylp-toluenesulfonate was heated in a 130° C. bath for 1 hr with stirring.The viscous material was cooled to an amorphous glass which washygroscopic. The yield ofbis(p-carbomethoxyphenyl)-phenylmethylphosphonium p-toluenesulfonate was26.1 g (92.5% of theory).

Anal. Calcd. for C₃₀ H₂₉ O₇ PS: C, 63.8; H, 5.2; P, 5.5; S, 5.7.

Found: C, 62.9; H, 5.2; P, 5.5; S, 5.7.

Structure confirmed by NMR.

PREPARATION 11 4-carbomethoxyphenylmethyldiphenylphosphonium3,5-bis(carbomethoxy)benzenesulfonate

A mixture of 16.0 g (0.05 mol) of p-carbomethoxyphenyldiphenylphosphineand 14.41 g (0.05 mol) of methyl 3,5-bis(carbomethoxy)benzenesulfonatewas heated in a 130° C. bath with nitrogen bubbling through the melt for2.5 hours.

Anal. Calcd. for C₃₁ H₂₉ O₉ PS: C, 61.2; H, 4.8; P, 5.1; S, 5.3.

Found: C, 61.3; H, 4.9; P, 5.0; S, 5.5.

PREPARATION 12 Methylbis(4-carbomethoxyphenyl)phenylphosphonium3,5-bis(carbomethoxy)benzenesulfonate

A mixture of 14.414 g (0.05 mol) of methyl3,5-bis(carbomethoxy)benzenesulfonate and 19.368 g (0.05 mol)bis(4-carbomethoxyphenyl)phenylphosphine was heated in a 130° C. bathwith nitrogen bubbling through the melt for 2 hours.

Anal. Calcd for C₃₃ H₃, O₁₁ PS: C, 59.5; H, 4.7; P, 4.6; S, 4.8.

Found: C, 59.6; H, 4.7; P, 4.7; S, 5.1.

Structure confirmed by NMR.

PREPARATION 13 Methylbis(4-carbomethoxyphenyl)phenylphosphoniumtetraphenylborate

A solution of 6.0 g (0.0115316 mol) ofmethylbis(4-carbomethoxyphenyl)phenylphosphonium iodide and 20 ml ofmethylene chloride was stirred rapidly with a solution of 3.95 g(0.0115316 mol) of sodium tetraphenylborate in 20 ml water for 2 hours.The organic layer was separated and washed with water, dried overmagnesium sulfate, and concentrated.

Yield: 6.7 g. Tg=60° C.

Anal. Calcd. for C₄₇ H₄₂ BO₄ P: C, 79.2, H, 5.9; B, 1.5; P, 4.3.;

Found: C, 78.9; H, 6.2; B, 1.1; P, 4.4.

Structure confirmed by NMR.

PREPARATION 14 Benzylbis(4-acetoxyphenyl)phenylphosphonium bromide

A mixture of 3.8 g (0.01 mol) of bis(4-acetoxyphenyl)phenylphosphine,1.7 g (0.01 mol) of α-bromotoluene and 15 ml of 1,1,1-trichloroethanewas heated to reflux at which time complete solution was achieved.Shortly thereafter, product began to precipitate from solution. Afterheating at reflux for 2.5 hr, the mixture was cooled, filtered and thesolid was washed with ether and dried. The yield ofbenzylbis(4-acetoxyphenyl)phenylphosphonium bromide was 5.0 g (90.0% oftheory); mp=233°-5° C.

Anal. Calcd. for C₂₉ H₂₆ BrO₄ P: C, 63.4; H, 4.8; Br, 14.5; P, 5.6.

Found: C, 62.7; H, 4.8; Br, 16.1; P, 5.5.

Structure confirmed by NMR.

PREPARATION 15 Methylbis(3-hydroxypropyl)phenylphosphoniump-toluenesulfonate

A solution 40.0 g (0.1768 mol) of bis(3-hydroxypropyl)phenylphosphineand 32.9 g (0.1768 mol) of methyl p-toluenesulfonate was stirred undernitrogen for 1 hr. The reaction was exothermic requiring no externalheating. The viscous product was then stored under nitrogen. The yieldof methylbis(3-hydroxypropyl)phenylphosphonium p-toluenesulfonate was71.0 g (97.4% of theory).

Anal. Calcd. for C₂₀ H₂₉ O₅ PS: C, 58.2; H, 7.1; P, 7.5; S, 7.8.

Found: C, 57.3; H, 7.3; P, 7.4; S, 7.9.

Structure confirmed by NMR.

PREPARATION 16 Ethylenebis(carbomethoxymethyldiphenylphosphonium)dibromide

To 3.98 g (0.01 mol) of bis(diphenylphosphino)ethane was added 3.06 g(0.02 mol) of methyl bromoacetate. After an initial exothermic reaction,50 ml of methylene chloride was added and the mixture was stirred for1.25 hr. The mixture was filtered and the collected solids were washedwith ether and dried. The yield ofethylenebis(carbomethoxymethyldiphenylphosphonium) dibromide was 1.0 g(14.2% of theory); mp=169°-70° C.

Anal. Calcd. for C₃₂ H₃₄ Br₂ O₄ P₂ : C, 54.6; H, 4.0; Br, 22.7; P, 8.8.

Found: C, 54.6; H, 4.9; Br, 22.2; P, 9.6.

Structure confirmed by NMR.

PREPARATION 17 Poly(neopentylene-co-pentaerythrityl 94.875/2.5terephthalate-co-adipate-co-methyldiphenyl-phosphonium-4-benzoatep-toluenesulfonate 94.75/5/0.25)

A mixture of 73.6 g (0.379 mol) of dimethyl terepthalate, 3.5 g (0.02mol) of dimethyl adipate, 58.3 g (0.56 mol) of neopentyl glycol, 0.51 g(0.001 mol) of methyl(4-carbomethoxyphenyl)diphenyl-phosphoniump-toluenesulfonate and 1.36 g (0.01 mol) of pentaerythritol was heatedin a polymer flask at 220° C. until molten with nitrogen bubblingthrough the melt. Tetraisopropyl orthotitinate (4 drops) was added andthe mixture was heated at 220° C. for 2 hr then at 240° C. for 1.5 hr.At this time, stirring was initiated and the pressure was reduced to0.30 mm Hg. Heating at 240° C. was continued for another 2.5 hr. Theyield of polymer was 83.5 g. The Tg was found to be 63° C. and theinherent viscosity in methylene chloride was 0.36.

PREPARATION 18 Poly[neopentylene-co-pentaerythrityl 95/2.5terephthalate-co-adipate-co-ethylenebis-(diphenylphosphonium-4-benzoate)di-p-toluenesulfonate 94.75/5/0.25]

In a polymer flask was placed 73.6 g (0.379 mol) of dimethylterephthalate, 3.5 g (0.02 mol) of dimethyl adipate, 58.3 g (0.56 mol)of neopentylglycol, 1.01 g ofethylenebis(4-carbomethoxyphenyldiphenylphosphonium) ditosylate and 1.36g (0.01 mol) of pentaerythritol. The mixture was melted in a 220° C.bath with nitrogen bubbling through the melt and 4 drops oftetraisopropyl orthotitanate was added. The mixture was heated for 2 hrat 220° C. and 1 hr at 240° C. The pressure was then reduced to 0.20 mmand with stirring, the mixture was heated at 240° C. for 2.5 hr andcooled. The inherent viscosity in methylene chloride was determined tobe 0.34 and the Tg was found to be 61° C.

PREPARATION 19 Poly[neopentyleneterephthalate-co-adipate-co-methylphosphoniumtris(4-benzoate)p-toluenesulfonate 87.5/5/5]

A mixture of 68.0 g (0.35 mol) of dimethyl terephthalate, 2.92 g (0.02mol) of adipic acid, 12.5 g (0.02 mol) ofmethyltris(4-carbomethoxyphenyl)-phosphonium p-toluenesulfonate and 58.3g (0.56 mol) of neopentylglycol was heated in a polymer flask at 220° C.until molten under nitrogen. Tetraisopropyl orthotitanate (4 drops) wasthen added and the mixture was heated at 220° C. for 2 hr, then at 240°C. for 1 hr. With stirring, the pressure was reduced to 0.10 mm Hg, andheating at 240° C. was continued for another 1 hr. The yield of polymerwas 83.5 g and the polymer exhibited an inherent viscosity in methylenechloride of 0.44 and a Tg of 66° C.

PREPARATION 20 Poly[neopentylene-co-pentaerythrityl 95/2.5terephthalate-co-adipate-co-methylphenylphosphonium bis(4-benzoate)p-toluenesulfonate 93.5/5/1.5]

In a polymer flask was placed 72.6 g (0.374 mol) of dimethylterephthalate, 3.5 g (0.02 mol) of dimethyl adipate, 3.39 g (0.006 mol)of methylbis(4-carbomethoxyphenyl)phenylphosphonium p-toluenesulfonate,58.3 g (0.56 mol) of neopentyl glycol and 1.36 g (0.01 mol) ofpentaerythritol. The mixture was then heated in a 220° bath until moltenat which time 4 drops of tetraisopropyl orthotitanate was added. Themixture was heated at 220° C. for 2 hr with nitrogen bubbling thrugh themelt and then at 240° C. for another 1.25 hr. The mixture was thenheated with stirring and an applied vacuum of 0.30 mm Hg for 3.5 hr andcooled. The yield of polymer was 84.5 g. The glass transitiontemperature was determined to be 65° C. and the inherent viscosity inmethylene chloride was determined to be 0.55.

PREPARATION 21 Poly(neopentylene-co-methylphenyldiphenylenephosphoniump-toluenesulfonate 90/10 isophthalate-co-adipate 90/10

A mixture of 21.09 g (0.09 mol) of poly(2,2-dimethyl-1,3-propyleneisophthalate) (IV=0.30 in phenol:chlorobenzene), 1.46 g (0.01 mol) ofadipic acid and 5.65 g (0.01 mol) ofmethylbis-(4-acetoxyphenyl)phenylphosphonium p-toluenesulfonate washeated in a 200° C. bath with nitrogen bubbling through the melt for 2hr. The mixture was then stirred at reduced pressure (0.30 mm Hg) foranother 2 hr at 230° C. and cooled. The glass transition temperature wasfound to be 60° C. and the inherent viscosity was determined to be 0.25in phenol: chlorobenzene.

PREPARATION 22 Poly[neopentylene methylphenylphosphoniumbis(-4-benzoate)p-toluenesulfonate]

A mixture of 5.64 g (0.01 mol) ofmethylbis(4-carbomethoxyphenyl)phenylphosphonium p-toluenesulfonate and2.08 g (0.02 mol) of neopentyl glycol was heated under nitrogen in a220° C. bath until molten. Tetraisopropyl orthotitanate (1 drop) wasadded, and the mixture was heated at 220° C. with nitrogen bubblingthrough the melt for 2 hr and at 240° C. for 1 hr. Stirring was theninitiated and the pressure was reduced to 0.30 mm Hg. Stirring andheating were continued at 240° C. for 2 hr after which the polymer wascooled. The inherent viscosity in methylene chloride was determined tobe 0.07 and the Tg was found to be 114° C.

Structure confirmed by NMR.

PREPARATION 23 Poly[1,2-propylene-co-glyceryl 92.5/5terephthalate-co-glutarate-co-methylphenylphosphoniumbis-(4-benzoate)tetraphenylborate 85/14/1]

A mixture of 3.56g (0.005 m) ofmethylbis(4-carbomethoxyphenyl)phenylphosphonium tetraphenylborate,11.21 g (0.07 m) of dimethyl glutarate, 82.53 g (0.425 m) of dimethylterephthalate, 2.3 g (0.025 m) of glycerol, and 49.21 g (0.648 m) of1,2-propanediol was heated under nitrogen to 220° C. until molten. 5drops of tetraisopropyl orthotitanate were added and heating continuedat 220° C. for 2.5 hours, then at 240° C. for 1 hour. Pressure wasreduced to 0.40 mm Hg, and heating continued for another 3.5 hours i.v.in DCM=0.43 dl/g. Tg=62° C.

PREPARATION 24 Poly[ethylene methylphenylphosphoniumbis(4-benzoate)p-toluenesulfonate]

Preparation was similar to Preparation 22. Inherent viscosity (i.v.) was0.05 in dichloromethane (DCM) and Tg was 115° C.

PREPARATION 25 Poly[1,4-dimethylenecyclohexanemethylphenylphosphoniumbis(4-benzoate) p-toluenesulfonate]

Preparation was similar to Preparation 22. The i.v. was 0.07 in DCM, andTg was 101° C.

PREPARATIONS 26-29

Polyesters were prepared in a manner similar to Preparation 19, usingthe monomers neopentyl glycol, dimethyl terephthalate, adipic acid, andmethylbis(4-carbomethoxyphenyl-phenylphosphonium p-toluenesulfonate inmolar ratios 100/n/5/m, respectively. Results are presented in Table I.

                  TABLE I                                                         ______________________________________                                                                   i.v. in DCM                                        Preparation                                                                              n      m        (dl/g)   Tg (°C.)                           ______________________________________                                        26         94.5   0.5      0.44     64                                        27         94     1.0      0.28     66                                        28         93.5   1.5      0.32     67                                        29         90     5.0      0.28     72                                        ______________________________________                                    

PREPARATIONS 30-33

Polyesters were prepared in a manner similar to Preparation 20, usingthe monomers neopentyl glycol, pentaerythritol, dimethyl terephthalate,dimethyl adipate, and methylbis(4-carbomethoxyphenyl)phenylphosphoniump-toluenesulfonate in molar ratios 95/2.5/n/5/m, respectively. Resultsare presented in Table II.

                  TABLE II                                                        ______________________________________                                                                   i.v. in DCM                                        Preparation                                                                            n        m        (dl/g)    Tg (°C.)                          ______________________________________                                        30       94.75    0.25     0.52      63                                       31       94.625   0.375    0.48      63                                       32       94.5     0.5      0.71      64                                       33       94       1        0.52      64                                       ______________________________________                                    

PREPARATIONS 34-36

Polyesters were prepared in a manner similar to Preparation 20, usingthe monomers neopentyl glycol, pentaerythritol, dimethyl terephthalate,dimethyl adipate, and methylbis(4-carbomethoxyphenyl)-phenylphosphoniump-toluenesulfonate in molar ratios n/m/94.5/5/0.5, respectively. Resultsare presented in Table III.

                  TABLE III                                                       ______________________________________                                                                  i.v. in DCM                                         Preparation                                                                              n     m        (dl/g)   Tg (°C.)                            ______________________________________                                        34         99    0.5      0.55     67                                         35         98    1.0      0.55     67                                         36         97    1.5      0.64     67                                         ______________________________________                                    

PREPARATION 37 Poly[1,2-propylene-co-pentaerythrityl 95/2.5.terephthalate-co-adipate-co-methylphenylphosphoniumbis-(4-benzoate)p-toluenesulfonate 94.5/5/0.5]

Preparation was similar to Preparation 20. i.v. in DCM=0.59 dl/g. Tg=72°C.

PREPARATIONS 38-39

Polyesters were prepared in a manner similar to Preparation 20, usingthe monomers ethylene glycol, 1,4-cyclohexanedimethanol, dimethylterephthalate, and methylbis(4-carbomethoxyphenyl)phenylphosphoniump-toluenesulfonate in molar ratios 70/30/n/m, respectively. Results arepresented in Table IV.

                  TABLE IV                                                        ______________________________________                                                                  i.v. in DCM                                         Preparation                                                                              n     m        (dl/g)   Tg (°C.)                            ______________________________________                                        38         99     1       0.22     68                                         39         75    25       0.07     46                                         ______________________________________                                    

PREPARATIONS 40-41

Polyesters were prepared in a manner similar to Preparation 20, usingthe monomers diethylene glycol, dimethyl terephthalate, andmethylbis(4-carbomethoxyphenyl)phenylphosphonium p-toluenesulfonate inmolar ratios 100/n/m, respectively. Results are presented in Table V.

                  TABLE V                                                         ______________________________________                                                                  i.v. in DCM                                         Preparation                                                                              n     m        (dl/g)   Tg (°C.)                            ______________________________________                                        40         95     5       0.18     23                                         41         80    20       0.08     38                                         ______________________________________                                    

PREPARATION 42 Poly[oxydiethylene-co-neopentylene 20/80terephthalate-co-methylphenylphosphoniumbis(4-benzoate)p-toluenesulfonate 90/10]

Preparation was similar to Preparation 20 i.v. in DCM=0.20 dl/g. Tg=75°C.

PREPARATION 43 Poly[neopentylene-co-pentaerythrityl 95/2.5terephthalate-co-adipate-co-methylphosphoniumtris(4-benzoate)p-toluenesulfonate 94.25/5/0.5]

Preparation was similar to Preparation 20 i.v.: in DCM=0.61 dl/g. Tg=64°C.

PREPARATION 44

A polyester was prepared in a manner similar to Preparation 21, usingadipic acid, bisphenol A, and 4-acetoxyphenylmethyldiphenylphosphoniump-toluenesulfonate in molar ratios 100/99.5/1. i.v. in DCM=0.13 dl/gTg=44° C.

PREPARATIONS 45-48

Polyesters were prepared in a manner similar to Preparation 21, usingthe monomers adipic acid, bisphenol A, andmethylbis(4-acetoxyphenyl)phenyl-phosphonium p-toluenesulfonate in molarratios 100/n/m, respectively. Results are presented in Table VI.

                  TABLE VI                                                        ______________________________________                                                                  i.v. in DCM                                         Preparation                                                                              n     m        (dl/g)    Tg (°C.)                           ______________________________________                                        45         99     1       0.19 (in DCM)                                                                           53                                        46         90    10       0.27 (in DCM)                                                                           69                                        47         50    50       0.16 (in P:CB)                                                                          --                                        48          0    100      0.09 (in DMF)                                                                           62                                        ______________________________________                                    

PREPARFATIONS 49-50

Polyesters were prepared in a manner similar to Preparation 21, usingthe monomers dimethyl terephthalate, adipic acid, neopentyl glycol, andmethylbis(4-acetoxyphenyl)phenylphosphonium p-toluenesulfonate in molarratios x/y/n/m, respectively. Results are presented in Table VII.

                  TABLE VII                                                       ______________________________________                                                                        i.v. in DCM                                   Preparation                                                                            x      y       n   m   (dl/g)    Tg (°C.)                     ______________________________________                                        49       94.05  5.95    99  1   0.17      57                                  50       90.25  9.75    95  5   0.18      53                                  ______________________________________                                    

PREPARATION 51 Poly(neopentylene-co-methylphenyldiphenylenephosphoniump-toluenesulfonate 99/1 terephthalate-co-cyclohexane-1,4-dicarboxylate89.1/10.9)

Preparation was similar to Preparation 21. i.v. in DCM=0.17 dl/g. Tg=60°C.

PREPARATION 52

A polyester was prepared in a manner similar to Preparation 21, usingthe monomers, adipic acid, bisphenol A diacetate, andmethyltris(4-acetoxy-phenyl)phosphonium p-toluenesulfonate in molarratios 100/98.5/1, respectively. i.v. in DCM=0.09 dl/g. Tg=31° C.

PREPARATION 53

A polyester was prepared in a manner similar to Preparation 18, usingthe monomers, dimethyl adipate, bisphenol A diacetate, andethylenebis(4-acetoxyphenyldiphenylphosphonium) di-p-toluenesulfonate inmolar ratios 100/75/25, respectively. i.v. in DCM=0.17 dl/g. Tg=67° C.

PREPARATION 54Poly[neopentylene-co-oxydiethylenebis(diphenyl-phenylenephosphonium)di-p-toluenesulfonate 99/1 terephthalate-co-adipate 94.05/5.95]

Preparation was similar to Preparation 18. i.v. in DCM=0.2 dl/g. Tg=62°C.

PREPARATION 55

In a polymer flask with open sidearm and teflon-coated bottom was placeda mixture of 90.8 g (0.4675 mol) dimethylterephthalate, 4.0 g (0.025mol) dimethyl glutarate, 3.04 g (0.005 mol)4-carbomethoxyphenyldiphenylmethylphosphonium3,5-dicarbomethoxybenzenesulfonate, 70.3 g (0.675 mol) neopentyl glycol,and 1.70 g (0.0125 mol) pentaerythritol. The mixture was then heated ina 220° C. bath under nitrogen until molten. 5 drops of tetraisopropylorthotitanate were added, and the mixture was heated at 220° C. withnitrogen bubbling through the melt for 2 hours and at 240° C. for 1hour. The mixture was then stirred at reduced pressure (0.50 mm Hg) for45 min at 240° C. and allowed to cool. i.v. in DCM=0.28 dl/g. Tg=65° C.

PREPARATION 56

A polyester was prepared in a manner similar to Preparation 55, usingthe monomers, dimethyl terephthalate, dimethyl glutarate,methylbis(4-carbomethoxyphenyl)phenylphosphonium3,5-dicarbomethoxybenzenesulfonate, neopentyl glycol, andpentaerythritol in molar ratios 93/5/1/95/2.5, respectively. i.v. inDCM=0.42 dl/g. Tg=66° C.

EXAMPLES 1-6 Toners and Developers

These examples illustrate the good charging properties of inventive dryelectrostatographic toners and developers. The polyesters ofPreparations 30, 32, and 33 were employed as dual functionbinder/charge-control agents. In Examples 1 and 4 the polyester ofPreparation 30 was employed. In Examples 2 and 5 the polyester ofPreparation 32 was employed. In Examples 3 and 6 the polyester ofPreparation 33 was employed.

In each example inventive toner particles were prepared bymelt-compounding 100 parts by weight of the polyester with 6 parts byweight of Regal 300™ pigment (a trademarked carbon black pigment sold byCabot Corporation, USA). This was accomplished by heating and mixing thepigment and polyester on a two-roll rubber mill, cooling the mass toroom temperature, and coarse grinding and fluid energy-milling toproduce toner particles having diameters in the range of 2 to 40micrometers. For each example the phosphonium salt charge-control moietyconcentration in moles per gram of total toner material was calculated.

In each example the toner particles were then mixed with carrierparticles in a closed container on a two-roll mill for several minutesto form an inventive triboelectrically charged two-component dryelectrostatographic developer comprising about 4 weight percent tonerparticles. The carrier particles employed in Examples 40-42 wereuncoated sponge iron particles, while in Examples 43-45 they were spongeiron particles coated with thin poly(vinylidene fluoride) film.

In each example the triboelectric charge per mass of toner particles wasthen measured in microcoulombs per gram (μc/g) by the "Blowoff" method.Results are reported in Table VIII.

                  TABLE VIII                                                      ______________________________________                                                           Phosphonium moiety                                                                            Toner                                                         Concentration in toner                                                                        charge                                     Example  Carrier   (moles/g)       (μc/g)                                  ______________________________________                                        1        uncoated  1 × 10.sup.-5                                                                           -3.1                                       2        uncoated  2 × 10.sup.-5                                                                           14.8                                       3        uncoated  4 × 10.sup.-5                                                                           33.7                                       4        coated    1 × 10.sup.-5                                                                           21.5                                       5        coated    2 × 10.sup.-5                                                                           41.5                                       6        coated    4 × 10.sup.-5                                                                           45.7                                       ______________________________________                                    

EXAMPLES 7-10 Charging capability compared to toners outside the scopeof the invention

In these examples the charge-control capability of polyesters in tonersof the invention is shown and compared to the capabilities ofcharge-control agents in toners outside the scope of this invention.

In each example and control the charge-control agent was melt-compoundedinto toner particles and mixed with coated carrier particles as inExamples 4-6. In each example and control the toner particles containedno added pigment or colorant, but the charge-control agent, whetherpolymeric or not, was mixed with an additional polyester, namely,poly(neopentylene-co-pentaerythrityl 95/2.5 terephthalate-co-glutarate95/5), in proportions sufficient to yield a concentration of 2.1×10⁻⁵moles of phosphonium salt charge-control moieties per gram of totalmaterial in the toner particles.

After mixing with poly(vinylidene fluoride)-coated strontium ferritecarrier particles, each toner's triboelectric charge was measured inmicrocoulombs per gram of toner (μc/g) by the "MECCA" method.

In control A, the only charge-control agent wasmethyltriphenylphosphonium p-toluenesulfonate, a non-polymericcharge-control agent employed in toners of the prior art.

In control B, the only charge-control agent was a polyester formed bypolycondensation of the monomers, dimethyl terephthalate, dimethylglutarate, methyltriphenylphosphonium3,5-dicarbomethoxybenzene-sulfonate, neopentyl glycol, andpentaerythritol in molar ratios 94/5/1/95/2.5, respectively. This is aphosphonium salt polyester, wherein only the anionic portion of the saltis covalently bonded to the polyester (by two ester linkages).

In Example 7, the only charge-control agent was a polyester useful intoners of the present invention, poly[neopentylene-co-pentaerythrityl95/2.5 terephthalate-co-glutarate-co-methylphenylphosphoniumbis(4-benzoate) p-toluenesulfonate 94/5/1], wherein only the cationicportion of phosphonium salt is bonded into the polyester (through twoester linkages).

In Example 8, the only charge-control agent was the polyester ofPreparation 55, wherein the cationic portion of the phosphonium salt iscovalently bonded to the polyester (through one ester linkage), and theanionic portion of the phosphonium salt is covalently bonded to thepolyester (through two ester linkages).

In Example 9, the only charge-control agent was the polyester ofPreparation 56, wherein both the cationic and the anionic portions ofthe phosphonium salt are covalently bonded into the polyester (eachthrough two ester linkages).

In Example 10, charge-control was provided by a 1 to 1 (by weight)mixture of the polyesters employed in control B and in Example 7 (i.e.,a mixture of a polyester with only the anionic portion of thephosphonium salt covalently bonded and a polyester with only thecationic portion of the phosphonium salt covalently bonded to thepolyester).

Results are presented in Table IX. Note again that all controls andexamples are developers having 2.1×10⁻⁵ moles of phosphonium saltmoieties per gram of total material in the toner particles.

                  TABLE IX                                                        ______________________________________                                                                     Toner Charge                                     Example                                                                              Nature of the Charge-Control Agent                                                                  (μc/g)                                        ______________________________________                                        Control                                                                              non-polymeric phosphonium salt                                                                      40.4                                             Control                                                                              polyester with only anionic                                                                         33.2                                             B      portion of the phosphonium salt                                               covalently bonded (2 bonds)                                            7      polyester with only cationic                                                                        67.3                                                    portion of the phosphonium salt                                               covalently bonded (2 bonds)                                            8      polyester with cationic portion                                                                     61.1                                                    of the phosphonium salt covalently                                            bonded (1 bond) and anionic portion                                           covalently bonded (2 bonds)                                            9      polyester with cationic portion of                                                                  61.2                                                    the phosphonium salt covalently                                               bonded (2 bonds) and anionic                                                  portion covalently bonded                                                     (2 bonds)                                                              10     1:1 mix of polyesters of control                                                                    55.8                                                    B and Example 7                                                        ______________________________________                                    

The data in Table IX show that covalently bonding the cationic portionof the phosphonium salt to a polyester yields a considerable increase incharge-control efficiency in the inventive toners over the correspondingnon-polymeric phosphonium salt charge agent. If the anionic portion ofthe cation-bonded phosphonium salt is also covalently bonded, or if thecation-bound polyester is mixed with an anion-only-bound phosphoniumpolyester, the charge-control efficiency is lessened somewhat but isstill considerably higher than the efficiency of the non-polymericphosphonium salt (thus providing convenient means for adjusting thecharge-control efficiency). The data also show that covalently bondingonly the anionic portion of the phosphonium salt to a polyester appearsto yield a considerable decrease in charge-control efficiency comparedto the corresponding non-polymeric phosphonium salt.

EXAMPLES 11-18 Charge level versus phosphonium salt moiety concentration(and comparison to non-polymeric phosphonium salts)

In these examples the charge level provided in inventive dry toners anddevelopers by the phosphonium polyesters is shown versus theconcentration of the phosphonium salt moiety in the toner, and thisperformance is compared to the corresponding non-inventive tonerscontaining non-polymeric phosphonium salt.

In these examples and controls, toner particles, and mixtures of themwith poly(vinylidene fluoride)-coated strontium ferrite carrierparticles to form charged developers, were prepared similarly toExamples 4-6, except that the carbon black pigment was included in thetoner particles in the proportion of 5 parts by weight pigment per 100parts polyester binder. Each developer's toner charge was measured inmicrocoulombs per gram of toner (μc/g) by the "MECCA" method.

The control toners and developers contained the polyester toner binder,poly(1,2-propylene-co-glyceryl 92.5/5 terephthalate-co-glutarate 86/14),and the prior art non-polymeric charge-control agent,methyltriphenylphosphonium p-toluenesulfonate, at various concentrationsof charge-control agent,

The toner particles in the inventive developers of Examples 11-14contained the inventive dual function polyester binder/charge-controlagent, poly[1,2-propylene-co-glyceryl 95/5terephthalate-co-glutarate-co-methylphosphoniumtris(4-benzoate)p-toluenesulfonate n/14/m]. The molar ratios, n/m, were: Ex.11=85.8125/0.125; Ex 12.=85.625/0.25; Ex 13.=85.25/0.5; and Ex.14=84.5/1.

The toner particles in the inventive developers of Examples 15-18contained the dual function polyester binder/charge-control agent,poly[1,2-propylene-co-glyceryl 92.5/5terephthalate-co-glutarate-co-methylphenylphosphonium-bis(4-benzoate)p-toluenesulfonate n/14/m]. The molar ratios, n/m, were: Ex.15=85.875/0.125; Ex. 16=85.75/0.25; Ex. 17=85.5/0.5; and Ex. 18=85/1.

Results are presented in Table X.

                  TABLE X                                                         ______________________________________                                                   Phosphonium salt moiety                                                       concentration in toner                                                                        Toner Charge                                       Example    (moles/g)       (μc/g)                                          ______________________________________                                        Control C  0               7.9                                                Control D  0.53 × 10.sup.-5                                                                        20.2                                               Control E  1.06 × 10.sup.-5                                                                        26.2                                               Control F  3.49 × 10.sup.-5                                                                        42.4                                               11         0.59 × 10.sup.-5                                                                        24.3                                               12         1.18 × 10.sup.-5                                                                        43.6                                               13         2.36 × 10.sup.-5                                                                        68.0                                               14         4.67 × 10.sup.-5                                                                        80.6                                               15         0.59 × 10.sup.-5                                                                        44.1                                               16         1.18 × 10.sup.-5                                                                        51.7                                               17         2.35 × 10.sup.-5                                                                        63.1                                               18         4.66 × 10.sup.-5                                                                        76.4                                               ______________________________________                                    

The results indicate the greater charge-control efficiency of thepolyesters in the inventive toners compared to the correspondingnon-polymeric prior art phosphonium salt charge-control agent and alsoindicate that greater changes in charge level are achievable by a givenincrease in the phosphonium salt moiety concentration in the inventivetoners than are achievable by the same concentration increase in thenon-inventive toners containing the prior art non-polymeric salts.

The invention has been described in detail with particular reference tocertain preferred embodiments thereof, but it should be appreciated thatvariations and modifications can be effected within the spirit and scopeof the invention.

What is claimed is:
 1. In an electrostatographic toner particle havingan average diameter in the range of 0.01 to 100 micrometers andcomprising a binder polyester and a charge-control agent comprising aquaternary phosphonium salt,the improvement wherein the phosphonium salthas a cationic portion comprising a phosphorus atom covalently bonded toat least one moiety containing an ester linkage to the binder polyester.2. The toner particle of claim 1, wherein the phosphonium salt has thestructure ##STR3## or the structure ##STR4## wherein: R¹, R², R³, and R⁴are each independently: alkyl which is unsubstituted, substituted withone or more aryl, or substituted with one or more group containing anester linkage to the binder polyester; or aryl which is unsubstituted,substituted with one or more alkyl, or substituted with one or moregroup containing an ester linkage to the binder polyester;R⁵ isalkylene, oxydialkylene, or arylenedialkylene; and A.sup.⊖ is an anion;with the provisos that: each alkyl or alkylene moiety recited above hasfrom 1 to 20 carbon atoms; each aryl or arylene moiety recited above hasfrom 6 to 14 carbon atoms; and at least one of R¹, R², R³, and R⁴contains at least one ester linkage to the binder polyester.
 3. Thetoner particle of claim 2, wherein R¹, R², R³, and R⁴ are eachindependently: alkyl which is unsubstituted or substituted with one ormore aryl; or aryl which is unsubstituted, substituted with one or morealkyl, or substituted with one or more group containing an ester linkageto the binder polyester; andwherein A.sup.⊖ has the structure

    .sup.⊖ O.sub.3 S--R.sup.6

wherein R⁶ is aryl which is unsubstituted or substituted with one ormore alkyl, halide, or group containing an ester linkage to the binderpolyester.
 4. The toner particle of claim 3, wherein the cationicportion of the phosphonium salt is monovalently appended to thepolyester through an ester linkage contained in R¹ of structure I. 5.The toner particle of claim 4, wherein the anionic portion of thephosphonium salt is divalently bonded into the polyester through twoester linkages contained in R⁶ of structure I.
 6. The toner particle ofclaim 3, wherein the cationic portion of the phosphonium salt isdivalently bonded into the polyester through ester linkages contained inR¹ and R² of structure I.
 7. The toner particle of claim 6, wherein theanionic portion of the phosphonium salt is divalently bonded into thepolyester through two ester linkages contained in R⁶ of structure I. 8.The toner particle of claim 3, wherein the cationic portion of thephosphonium salt is divalently bonded into the polyester through twoester linkages contained in R¹ of structure I.
 9. The toner particle ofclaim 3, wherein the cationic portion of the phosphonium salt isdivalently bonded into the polyester through ester linkages contained inthe two R¹ groups of structure II.
 10. The toner particle of claim 3,wherein the cationic portion of the phosphonium salt is trivalentlybonded into the polyester through ester linkages contained in R¹, R²,and R³ of structure I.
 11. The toner particle of claim 1, furthercomprising a second binder polyester.
 12. The toner particle of claim 1,further comprising a second binder polyester containing a quaternaryphosphonium salt having an anionic portion containing at least one esterlinkage to the second binder polyester.
 13. The toner particle of claim1, further comprising a colorant.
 14. In a dry electrostatographicdeveloper comprising:(a) carrier particles and (b) toner particles, theimprovement wherein the toner particles are as defined in claim 1.